blob: c4d07cfbb1fa54d6a7b84c40e5d4c69252bb7b4a (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
|
{ depot, pkgs, ... }:
# Atomically write a file (just `>` redirection in bash
# empties a file even if the command crashes).
#
# Maybe there is an existing tool for that?
# But it’s easy enough to implement.
#
# Example:
# atomically-write
# ./to
# echo "foo"
#
# will atomically write the string "foo" into ./to
let
atomically-write = pkgs.writers.writeDash "atomically-write" ''
set -e
to=$1
shift
# assumes that the tempfile is on the same file system, (or in memory)
# for the `mv` at the end to be more-or-less atomic.
tmp=$(${pkgs.coreutils}/bin/mktemp -d)
trap 'rm -r "$tmp"' EXIT
"$@" \
> "$tmp/out"
mv "$tmp/out" "$to"
'';
in
atomically-write
|
